Background: Key reasons for the "quality chasm" between current and ideal chronic illness care are that our health care system is insensitive to patient preferences, provider-driven, and disease-focused. By contrast, a common goal among proposed patient-centered care models is to foster continuous healing relationships between patients and the health care system. Such relationships allow patients to receive care over time via a variety of communication media, rather than just via episodic office visits. Home health care can foster such relationships and improve outcomes for patients with a variety of conditions. Home interventions may be particularly useful in caring for the growing number of people with chronic illnesses and accompanying functional limitations that might limit their access to community-based interventions. However, trials comparing the effectiveness and cost-effectiveness of the wide array of home care models are limited, and the mechanisms that underlie their effectiveness remain unclear. Aims/Hypotheses: This study will address these research gaps. The study hypotheses are: a) Each of three home interventions will result in improvements in patient self-efficacy, adherence to care, and health-related quality of life (HRQOL) compared with usual care but will not differ statistically; b) From the payer's perspective, all the interventions will be cost saving compared with usual care, and a standard telephone intervention will be the most cost saving; and c) Self-efficacy will improve temporally before adherence to care and HRQOL. Methods: This will be a randomized controlled study of four groups, comparing the effectiveness and incremental cost-effectiveness of three different home-based care models and usual care in improving chronic illness outcomes. The chronic illnesses targeted will be arthritis, asthma, chronic obstructive pulmonary disease, congestive heart failure, depression, and diabetes mellitus. Trained laypersons will deliver the interventions, a self efficacy enhancement program (vs. usual care). The home care delivery media in the models will be in person visits, videophone calls, and standard telephone calls. The primary outcomes will be HRQOL and costs. Implications: Better understanding of the mechanisms of effectiveness of home care will facilitate the development of optimal home interventions. The findings will help policymakers, payers, and providers identify which interventions to implement.